1. Field of the Disclosure
This disclosure relates generally to drilling motors for use in drilling of wellbores.
2. Brief Description of the Related Art
To obtain hydrocarbons, such as oil and gas, boreholes or wellbores are drilled by rotating a drill bit attached to a drill string end. A substantial proportion of the current drilling activity involves drilling deviated and horizontal boreholes to increase the hydrocarbon production and/or to withdraw additional hydrocarbons from the earth's formations. Directional drilling systems generally employ a drill string having a drill bit at the bottom that is rotated by a positive displacement motor (commonly referred to as a “mud motor” or a “drilling motor”). A typical mud motor includes a power section that contains a stator and a rotor disposed in the stator. The stator typically includes a metal housing lined inside with a helically contoured (lobed) elastomeric material. The rotor is typically made from a suitable metal, such as steel, and includes lobes on its outside surface. Some mud motors include a metallic stator and a metallic rotor. Pressurized fluid (commonly known as the “mud” or “drilling fluid”) is pumped into a progressive cavities formed between the rotor and stator lobes. The force of the pressurized fluid pumped into the cavities causes the rotor to turn in a planetary-type motion. In the metal-metal stator and rotor mud motor, a clearance is designed between the rotor and stator to allow assembly of the mud motor. Such a construction loses efficiency as the drilling fluid flows across the clearance between the cavities. The efficiency of such metal-metal mud motors is typically lower than a rubber stator and metal rotor mud motor due to the lack of sealing between the rotor and stator.
The disclosure herein provides metal-metal mud motors with an interference seal between the rotor and the stator.